Disposable shield medical syringe

Abstract

A disposable shielded medical syringe wherein the contaminated needle is connected to a piston slidably mounted in the syringe barrel. The syringe plunger piston is threadably connectable to the needle piston for pulling the contaminated needle into the barrel to the shielded position. The syringe plunger is disconnectable from the plunger piston after the needle has been moved to the shielded position and a cap is insertable into the open end of the syringe barrel to completely enclose the contaminated needle.

We claim: 
     
       1. A disposable shielded medical syringe comprising a syringe barrel, a plunger slidably mounted in said barrel, a piston secured to the distal end of the plunger and being in sealing, sliding engagement with the inner wall of the barrel, a second piston slidably mounted in said barrel and being in sealing, sliding engagement with the inner wall of the barrel and being positioned between the distal end portion of the barrel and the plunger piston, a syringe needle extending outwardly longitudinally of the barrel at the distal end thereof, means for detachably connecting the syringe needle to said second piston, means for mechanically connecting said plunger piston to said means for connecting the syringe needle to said second piston, said second piston having a configured outer surface cooperating with a similarly configured inner surface on the distal end of said barrel, to thereby prevent the second piston from rotating within the barrel when the needle is being operatively connected thereto and also preventing the second piston from rotating within the barrel when the plunger piston is being operatively connected thereto, and a medicament contained within the barrel between the plunger piston and the second piston, whereby the medicament is dispensed through the needle by pushing the plunger inwardly, whereupon the plunger piston is mechanically connected to the means for connecting the syringe needle to said second piston, and the second piston and associated contaminated needle is drawn inwardly to a shielded position within the barrel by pulling the plunger in a direction toward the proximate end of the barrel. 
     
     
       2. A disposable shielded medical syringe according to claim 1, wherein the means for connecting the syringe needle to the second piston comprises, a Luer Lock member operatively connected to said second piston, said needle having a Luer Lock hub portion, said needle Luer Lock hub portion being threadably connected to said Luer Lock member. 
     
     
       3. A disposable shielded medical syringe according to claim 2, wherein the means for mechanically connecting the plunger piston to the Luer Lock member comprises a threaded projection extending axially from the plunger piston, and a similarly configured threaded aperture provided in said Luer Lock member. 
     
     
       4. A disposable shielded medical syringe according to claim 1, wherein a needle cap is insertable into the open end of the barrel to prevent the contaminated needle from being moved from the retracted, shielded position outwardly through the open end of the barrel. 
     
     
       5. A disposable shielded medical syringe according to claim 1, wherein spring stop means are mounted on the proximate end portion of the barrel adapted to be engaged by the syringe piston when fully retracted to thereby prevent complete removal of the syringe piston from the barrel. 
     
     
       6. A disposable shielded medical syringe according to claim 1, wherein connecting means are provided between the plunger and plunger piston, whereby the plunger is disconnected from the plunger piston after the contaminated needle is moved to the shielded position. 
     
     
       7. A disposable shielded medical syringe comprising a syringe barrel, a plunger slidably mounted in said barrel, a piston secured to the distal end of the plunger and being in sealing sliding engagement with the inner wall of the barrel, a second piston slidably mounted in said barrel and being in sealing, sliding engagement with the inner wall of the barrel and being positioned between the distal end portion of the barrel and the plunger piston, a syringe needle extending outwardly longitudinally of the barrel at the distal end thereof, means for connecting the syringe needle to said second piston, means for mechanically connecting said plunger piston to said means for connecting the syringe needle to said second piston, and a medicament contained within the barrel between the plunger piston and the second piston, said second piston having a polygonal outer surface, the distal end portion of the barrel having a polygonal inner surface cooperating with the polygonal outer surface on the second piston, whereby the second piston is prevented from rotating within the barrel when the needle is being operatively connected to said second piston. 
     
     
       8. A disposable shielded medical syringe of the type wherein the syringe needle is retracted into the syringe barrel through the open end of the barrel, the improvement comprising spring stop means mounted on the proximate end portion of the barrel adapted to be engaged by the syringe piston when fully retracted to thereby prevent complete removal of the syringe from the barrel, the syringe piston including a plunger having a threaded stem portion threadably mounted in a threaded hub portion on the piston whereby the plunger can be disconnected from the piston when the piston has been moved to the retracted position, radially extending arms on said hub portion, portions of the spring stop means being engageable with said arms to thereby prevent rotation of the piston during the disconnecting of the plunger therefrom. 
     
     
       9. A disposable shielded medical syringe comprising a syringe barrel, a plunger slidably mounted in said barrel, a piston secured to the distal end of the plunger and being in sealing sliding engagement with the inner wall of the barrel, a second piston slidably mounted in said barrel and being in sealing, sliding engagement with the inner wall of the barrel and being positioned between the distal end of the barrel and the plunger piston, a syringe needle extending outwardly of the barrel at the distal end thereof, means for connecting the syringe needle to said second piston, and a medicament contained within the barrel between the plunger piston and the second piston, said second piston having a polygonal outer surface, the distal end portion of the barrel having a polygonal inner surface cooperating with the polygonal outer surface on the second piston, whereby the second piston is prevented from rotating within the barrel when the needle is being operatively connected to said second piston.